Targeting cancer and SARS-CoV-2: phytochemical, biological and molecular dynamic investigations of Sargassum aquifolium and Galaxaura rugosa

This study aimed to acquire in-depth phytochemical and biological insights into the different extracts of Sargassum aquifolium and Galaxaura rugosa, due to the limited existing data on these species. GC/MS analysis of the unsaponifiable matter identified 27 compounds in S. aquifolium, including three phytosterols and two fatty alcohols, while G. rugosa contained 23 compounds. Fatty acid methyl ester profiling revealed six fatty acids in S. aquifolium and 21 in G. rugosa. Isolation led to the identification of six compounds from S. aquifolium (including two sterols and two fatty alcohols) and seven from G. rugosa (with two sterols). GLC analysis showed rhamnose and galactose as the major sugars in S. aquifolium, and mannose, arabinose, and glucose in G. rugosa. HPLC detected 17 amino acids across both species. LC/MS profiling of pigment extracts revealed 13 pigments, 11 sterols, and 17 terpenoids in S. aquifolium, and 16 pigments, 9 sterols, and 12 terpenoids in G. rugosa. Among the various extracts, the pet. ether extract of S. aquifolium exhibited the highest antioxidant activity, whereas that of G. rugosa demonstrated potent antiviral activity against SARS-CoV-2 (IC₅₀ = 6.454 µg/mL). Notably, the aqueous and pigment extracts of S. aquifolium showed significant cytotoxicity against lung cancer cells (inhibition rates of 70% and 62.56%, respectively). Furthermore, aqueous extracts of S. aquifolium and G. rugosa exhibited strong activity against colon cancer cells (76.02% and 61.17% inhibition, respectively). Molecular docking studies highlighted phytol as a potential bioactive compound contributing to these therapeutic effects. These findings suggest that pet. ether extracts could be promising sources of antioxidant and antiviral agents, while the aqueous and pigment extracts of S. aquifolium may hold therapeutic potential against lung and colon cancers.